


Simple Biology

by shirasade



Series: Biological Imperative [1]
Category: Shadowhunters (TV)
Genre: Alpha Alec, Alpha/Omega, Alternate Universe, Angst and Fluff and Smut, First Time, M/M, Omega Jace, POV Jace Wayland, Teenagers
Language: English
Status: Completed
Published: 2017-09-08
Updated: 2017-09-08
Packaged: 2018-12-25 07:49:15
Rating: Explicit
Warnings: Underage
Chapters: 1
Words: 7,382
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/12031410
Author URL: https://archiveofourown.org/users/shirasade/pseuds/shirasade
Summary: Everyone, including Jace himself, had expected him - strong, cocky, possibly the most gifted Shadowhunter of his generation - to present as an alpha.





	Simple Biology

**Author's Note:**

> I never thought a/b/o would be something I write, yet here I am... This was supposed to be a PWP, but I wanted to make it mostly canon-compliant, so the angst couldn't really be avoided. Also, I tried to avoid the pitfalls of unbalanced power dynamics (especially because they're both teens), but this _is_ the story of Jace's first heat, so proceed accordingly. ;)
> 
> For Jalec Sexy September week 2 - kinks.

They were sparring as they often did, both of them relishing the challenge, when Alec suddenly stopped in mid-swing, so abruptly he almost caught Jace’s elbow in the face. 

"What?!" Jace asked, annoyed, but Alec just sat there in wide-eyed shock, nostrils flaring. 

Sniffing the air, Jace caught a whiff of Alec's familiar alpha scent mingled with his own - but in addition to the expected sweat an unmistakable odor of _omega_ hung in the air around him. Heart dropping into this stomach Jace realized what had happened, and he barely managed to hold it together long enough to hiss through gritted teeth, "Don't you dare say a word!"

With that he whirled around and raced off, desperate to get away. In his head his father's words about weak, useless omegas reverberated, and despite himself Jace could feel tears prick behind his eyelids as he stumbled into his room and slammed the door shut.

Everyone, including Jace himself, had expected him - strong, cocky, possibly the most gifted Shadowhunter of his generation - to present as an alpha. Ever since Jace had turned 15 a few weeks ago they’d waited for the tell-tale signs of alpha maturity, the ones that Alec had exhibited a year previously, expecting him to be early in this as he was in everything else. 

Now Jace was tearing off his clothes in a frenzy, his mind a frantic litany of _Nononono, this isn’t possible, it can’t…_ as he jumped into the shower and set the water to scalding hot, scrubbing himself down as if that way he could get rid of the scent that was clinging to his skin. Squeezing his eyes shut, Jace reached around himself with trembling fingers, hesitating for a long moment before roughly spreading his cheeks and jabbing a finger inside his opening. 

He was too violent, and the pain burned through him, but before he could convince himself that this was a sign that nothing had changed his fingertip found the unmistakable bump of a gland that hadn’t been there before. Or rather, it hadn’t been noticeable before, undeveloped, and when a drop of lubrication coated the questing digit Jace bit his lip so hard it bled. He withdrew his hand painfully fast, but he was grateful for the burning sensation, his mind shying away from the small burst of pleasure he’d felt even through the discomfort.

Squirting half a bottle of body wash over his hand, he scrubbed and scrubbed at the tiny speck of viscous fluid until he could no longer see or smell this irrefutable proof of his new status on his fingers, then he poured the rest of the soap over his back, making sure to coat his scent gland at the nape of his neck. Finally he could no longer smell any trace of omega, of _weakness_ , and Jace left the shower on wobbly legs, feeling completely drained, as if he’d just gone three rounds against Hodge or woken from yet another nightmare of his father. Wrapping himself in a towel from head to toe, not wanting to catch even a glimpse of the body that had betrayed him, he left the bathroom - and stopped in his tracks when he caught sight of Alec. 

His friend’s head shot up, and he made as if to reach out, eyes full of concern, but Jace drew back sharply, and Alec’s hand dropped to his side resignedly. Tightening the towel around himself, Jace half-yelled, “What are you doing here? I don’t want you here, I don’t want _anyone_!” Dropping his voice he added venomously, “Come to gloat?”

“I… what?!” Alec looked as hurt as Jace had viciously hoped for, but then he visibly composed himself and said simply, “Of course not, don’t be stupid. Why would I, there’s nothing wrong with being an omega. But you seemed… upset, I just wanted to make sure you’re okay.”

He didn’t _appear_ to be lying, and Jace took a deep breath, trusting his sense of smell more than his eyes, but there was no trace of deceit in the air, only worry and that comforting, warm spiciness that was uniquely Alec - and uniquely _alpha_. Whirling away, Jace bought time by pulling out some fresh clothes while his mind raced. He’d always liked the way Alec smelled, but now he hated it, hated that he had to wonder whether it had been his _omeganess_ that made him want to trust Alec, that had made him want to ask him to be his parabatai once he presented.

Laughing joylessly, Jace swallowed down bitter disappointment. Blindly putting on sweats and a long-sleeved shirt, he finally forced himself to face Alec, who’d been watching him quietly, and bit out, “Okay? Yeah, sure. I’m a useless fucking _omega_ but I’m okay. So you can go and be an overprotective alpha somewhere else.”

Confusion clouded Alec’s gaze, but Jace refused to weaken, crossing his arms in front of himself defiantly and waiting for Alec to either dismiss or patronize him as a hysterical omega. Instead, Alec’s face cleared, and he rolled his eyes in exactly the same, fond way he always did when he thought Jace was being overly dramatic. “Are you done? I don’t know what your father told you, but I think I can guess - and I’m sorry, but he was full of _shit_ if he told you that omegas are somehow weaker or worth less or whatever.” Crossing the room he stopped in front of Jace, who had to fight the urge to back away, and rested a hand on Jace’s arm, voice full of warmth as he said, “You’re still you, Jace, and I’m still me, and we’re going to get through this - _together_ , deal?”

Despite himself Jace found himself nodding, a small tendril of hope taking root. This was why he wanted Alec to be his parabatai, because as good as Jace knew he was on his own, with Alec he was better. Even now he knew deep down that Alec was being sincere, that for him really nothing had changed. Jace’s grin felt wobbly on his lips, but the answering smile on Alec’s face was warm enough to turn his own more genuine, and he sounded almost normal as he replied, “Deal. But if you ever treat me like an omega I’ll kick your ass so hard you won’t remember your name!”

“Well, you can _try_...” Alec’s smirk was wonderfully normal, familiar, and some of the tension Jace had been holding in his body bled out of him. It came rushing back, however, when Alec added apologetically, “You’ll have to see a doctor, though, just like I did - and good luck trying to keep mom and Izzy from throwing you a presentation party!”

In the end Jace agreed to a small family gathering, although he still had trouble accepting that none of the Lightwoods thought any less of him, and neither did anyone at the Institute appear to change their behavior towards him once the news spread. Maryse was an alpha like her oldest son, and Robert was a very competent beta, but now Jace noticed for the first time that there were several omegas among the Shadowhunters, and no one treated them any differently. When he said as much to Alec, his friend gave him a long look. “Shadowhunters aren’t perfect, but we’re not stupid. This is our biology, a gift from the angel.”

Jace still wasn’t thrilled that his body had betrayed him in this fashion, and he did his best to ignore the changes, but after a few months passed without further humiliating incidents he stopped worrying about it too much, putting his focus back on training. And if he exercised just a bit harder and sparred just a bit more relentlessly, not even Alec felt tempted to point it out. Jace even began to once again consider asking Alec to be his parabatai.

Which was when his first heat hit, the sign that he’d reached full maturity.

It started with a growing sense of unrest, as if his skin was too tight on his bones, and his senses sharpened until everything seemed too bright, too loud, and he had no choice but to admit to himself what was happening. The doctor had prepared him for it, although she’d been unable to tell him when his body would be ready, and truth be told Jace had tried his best to ignore the fact that for the rest of his fertile days he’d be suffering from the omega equivalent of bad periods - well, ovulation, to be exact, but ovulation in mundane women didn’t incapacitate them.

Like most omegas in modern times Jace would be taking suppressants most of the year, but the doc had made it quite clear that it was important that his first heat ran its natural course, and that he’d have to go through one cycle without blockers at least once a year if he wanted to stay healthy. He already hated it, not used to his body asserting that kind of control over him, and Jace found himself pacing restlessly around the roof. He’d been forced to flee the training room, where he’d been trying to exhaust himself, when Hodge had stuck his annoying alpha head through the door and taken one sniff of the pheromone-laden air, eyes darkening before he’d shaken himself and backed away. The worst thing, however, had been that for one dreadful second Jace had wanted to fling himself at the older man, which had led to his desperate flight.

“I hope you’re not planning to do something stupid.” Alec’s voice cut through the cool autumn air, making Jace jump, cursing himself for not paying attention. The next moment Alec’s familiar scent flooded his senses, and he grit his teeth and turned his face into the wind, hating the way his stupid instincts told him to wrap himself around his friend, let him soothe the itch that kept building under his skin.

“Did Hodge tattle on me?” His question was more of an accusation, although he knew that he was being irrational. If there was any time to be irrational, this was it, after all.

Alec didn’t let it faze him, however, leaning against the far wall - making sure to stand against the wind, as Jace noticed, grateful for the consideration in spite of himself. “He just wants you to be safe.” He paused, and although his position meant that Alec doubtlessly got the full load of Jace’s increased pheromones, the hazel eyes remained calm. “This is the 21st century, Jace. No one is going to force you to do anything you don’t want to. If you want, you can spend the next couple of days in your room, and Izzy or one of the other kids that haven’t presented yet will look after you.” A flush crept into Alec’s cheeks as he added quickly, “There’s… toys you can use, too.”

Tearing his eyes away, Jace felt himself blush and crossed his legs, his voice rough as he asked, “Is that what you did?”

He’d been around for Alec’s first rut, but he’d never actively thought about what Alec had been doing locked in his room for three days. Now he couldn’t stop the mental images from rising, and he had to grip the parapet to stop his hands from wandering downwards, where he could feel a traitorous wetness between his legs while his cock thickened as blood rushed south.

Behind him, he heard Alec take a shuddering breath, and humiliation flooded him along with his growing arousal, knowing that the alpha had no choice but to smell exactly what was going on with him. However, when Alec spoke he sounded pointedly normal. “Yes. I… I didn’t want my first time to be with… with someone I wouldn’t normally want.”

That was such an Alec reaction, and fondness for his friend rolled through Jace, although he forced himself to keep his voice light as he teased, “Ha, I _knew_ you’re still a virgin!”

“Oh, shut it, not everyone can be a manwhore like you,” Alec grumbled, but there was no bite to it, just their regular level of insult, and Jace clung to this semblance of normalcy. It lasted right until he turned around and saw the way Alec’s hazel eyes tracked over his body helplessly before being fixed determinedly at some point over Jace’s shoulder. 

A pink tongue darted out to wet dry lips, which Jace had never noticed were plump and inviting, and Jace suddenly wondered what Alec would taste like. Squeezing his eyes shut, he closed his hands into fists, hoping the pain of blunt nails digging into his palms would help, but instead his treacherous brain supplied him with mental images of Alec’s long, strong archer’s fingers wrapping around… around… Jace snapped his eyes open with a strangled gasp and found Alec staring at him with unmistakable hunger.

“I should go,” the alpha said roughly, as if he had to force the words out, his entire posture screaming of his desire to do the opposite, but Jace knew without a doubt that Alec would leave immediately if Jace asked him to. His gaze flicked down Alec’s body helplessly, to the bulge clearly visible through black sweatpants; it was only for a moment but he knew he’d been caught when something like a _growl_ escaped Alec, making the hairs on the back of Jace’s neck stand up. “Now. I’m going _now_.”

Still, for a long moment he remained frozen in place, eyes that were dark with arousal locked on Jace, who had to forcibly hold back a whine that wanted to claw its way from his throat. It felt as if his entire body was vibrating with the need to rush forward, stop his friend from leaving. Then Alec finally wrenched his gaze away and turned to leave - and that proved to be the last straw.

“No!” Jace heard himself calling out, hating the edge of desperation in his voice. Alec stopped in his tracks, confusion clouding his face, and before he lost his courage Jace added quickly, “Can you… would you help me? I don’t think I want to go through this alone, and I _trust_ you, Alec.”

Once the words were out, Jace immediately felt less tense, albeit not any less turned on. He didn’t even mind that Alec didn’t answer immediately, appreciating that his friend rarely jumped into anything that mattered without giving it its due consideration. And no matter how much Jace’s instincts screamed for him to just launch himself at Alec, he was still lucid enough to know that this was no small thing, especially considering the fact that unlike Jace Alec was a virgin. 

“It’s alright if you’d rather not,” Jace said softly, even if a big part of his brain didn’t agree.

He hadn’t expected the wry snort that escaped Alec, which seemed to be directed mostly at himself. “Yeah, no, I want to, that’s not the issue. It’s just - are you sure, Jace? I know you weren’t exactly thrilled when you presented as omega, and if we do this...”

Anticipation was a tingle at the base of Jace’s spine, and he smiled, almost giddy with relief. Giving in to his impulses, he stepped closer to Alec, almost moaning when a cloud of aroused alpha scent reached his nostrils, and his voice was hoarse as he replied, “That’s why it can only be you. I know you won’t treat me any differently after.”

 _After_. Jace didn’t particularly feel like thinking too hard about anything except the immediate future, not when Alec was right there, barely a foot away, all alpha and barely suppressed hunger. Deciding that they’d done all the talking that was necessary, he licked his lips, gratified when Alec tracked the movement with wide eyes, pupils blown and breaths shallow. The air crackled between them, but when Alec closed the remaining distance between them it was with deliberate care, and his hands were gentle on Jace’s face. 

Then he nodded, and it felt like a start signal. Moving simultaneously they surged forward, lips and bodies colliding with the force of pheromone-fuelled desire. Jace could have wept with relief, Alec’s taste and scent enveloping him like a blanket, bringing the need burning inside him down to a manageable level. And much to Jace’s surprise his innocent friend could _kiss_ , mouth sure and insistent against Jace’s own, as if he was intent on driving Jace out of his mind systematically, switching between teasing brushes and hard, claiming kisses, using his tongue just right, not too much and not too little. Groaning, Jace slid his hands into Alec’s hair, pushed his body forward against the hard planes of the alpha’s body, so familiar from years of training and changing in front of each other - and yet all of a sudden it felt like a foreign country, one Jace couldn’t wait to explore.

When Alec broke their kiss, Jace tried to chase after him, but Alec rested their foreheads together, hands firm on Jace’s upper arms, and managed to say through panting breaths, “We have to get inside. Before we’re too far gone.”

Reluctantly Jace had to admit that Alec was right. As enticing as the prospect of just ripping off their clothes and having sex right here on the roof was, the doctor had made it quite clear that his first heat would last at least several hours, maybe even days. Relocating to somewhere sheltered, within easy reach of food, drink and anything else they might need, was obviously the right course of action. Jace pushed his nose against Alec’s neck one last time, letting his scent wash over him, and then tore himself away, fighting every instinct in his body.

“You go ahead to your room,” Alec instructed, voice satisfyingly hoarse. “I’ll just let mom know where we’ll be and grab some provisions.”

Jace nodded, for once not in the mood to argue, and had to suppress an undignified squawk when Alec suddenly reached out and pulled him into another kiss, rough and claiming, before half-pushing Jace away with a frustrated growl. They were both breathing hard, faces flush with arousal, and Jace didn’t think he’d ever been this hard in his life. Or this _wet_ , having so far rather studiously avoided this new _thing_ his body could do. Squashing the urge to throw himself back into Alec’s arms, he cursed and whirled around, making his way downstairs at a half-run.

Luckily he didn’t meet anyone, not in the mood to explain himself, even if rationally he knew his fellow Shadowhunters were much more likely to congratulate than mock him. He had intended to head to his room, as Alec had suggested, but when he passed the door to the alpha’s room a whiff of that warm, slightly spicy smell that was uniquely Alec caught his attention. Without thinking he changed course and entered, tension he hadn’t been aware of draining from him as he flung himself onto his friend’s neatly made bed. Jace groaned and rubbed his entire body against the mattress, the scent of _Alec_ and _alpha_ both comforting and arousing.

Burying his nose into Alec’s pillow, Jace let his hands wander down his body, his skin so sensitive, his clothes were beginning to chave uncomfortably. He didn’t hesitate to tear off his shirt and wriggle out of his jeans, sighing in relief when his fingers closed around his leaking cock. He tugged a few times, but although it felt good - more than good - he couldn’t reach the point of orgasm, the familiar pressure of his grip somehow not _enough_. 

Going by instinct, Jace slid one hand past his balls, only hesitating for a second when he encountered the wetness of his slick that had already started to pool underneath him. Taking a deep breath Jace let Alec’s scent wash away the last of his reluctance and breached himself. He’d expected resistance, maybe even pain, but instead his finger went in easily, and Jace moaned, canting his hips so he could reach deeper, touch nerve endings already humming with excitement. A fresh surge of wetness seeped out of him, and Jace scooped up some of it with his other hand, used it to jerk himself off in counterpoint to the rhythmic in-and-out of two, then three fingers. 

It felt so _good_ , and Jace was long past the point of caring what he looked like, spread out naked on Alec’s bed with one hand in his ass, fucking himself as wave after wave of pleasure ran through him. It didn’t take long and he was coming, back arching, coating his stomach and the mattress with cum and slick, the world whiting out for an instant as he fell back onto the bed, boneless with contentment, heat satisfied for the moment.

“Fuck, _Jace_!” Alec’s growl, a good half-octave deeper than his normal tone, brought Jace out of his stupor, but his head was still too fuzzy to feel more than vaguely self-conscious. Especially since Alec was standing in the door staring at him like he was good enough to eat, one hand frozen on the handle behind him, the other holding a heavy-looking bag in a white-knuckled grip, his entire body vibrating with _need_ , as if he was holding himself back by sheer force of will. Clearing his throat, he added inanely, “I thought you were going to be in _your_ room.”

Chuckling, Jace spread himself out further, ignoring the uncomfortable stickiness, and gestured around himself. “So much nicer here. Also, you get to clean it.”

The laugh that escaped Alec sounded halfway normal, although still with an edge of hunger to it that made Jace shiver slightly. Warmth was beginning to pool in his stomach again, and he took an unsteady breath, fingers tightening around his cock. Alec was watching him with dark eyes, but then he shook himself, looking away, and Jace felt suddenly cold, wanting his attention back on him. Well, more than just his attention, but for the next few minutes Alec stiffly ignored him, busying himself with emptying his bag, setting bottles of gatorade and snack bars onto the bedside table as well as packets of lube and… 

“Are those _toys_? Alec Lightwood, did you bring me sex toys?” Jace gave a strangled laugh, by now jerking himself off in earnest.

Alec froze, ears bright red, and turned away, crossing to the bathroom quickly, explaining over his shoulder, “Well, I know you said you wanted me to… to help, but we don’t have to - you know…”

Alec’s continued thoughtfulness would have been sweet if it wasn’t so frustrating, when all Jace wanted was for Alec to stop being so damn considerate and finally _touch_ him. Still, when Alec returned with a warm, wet cloth, Jace’s eyes slid shut in bliss, and he let himself be cleaned by gentle, thorough hands. Alec’s proximity made his body sing, and by the time Alec finally dropped the washcloth, Jace was simultaneously bonelessly relaxed and incredibly turned on. 

Smiling lazily up into Alec’s warm hazel eyes, he reached up and trailed a hand down Alec’s cheek, stopping at his lips, which parted in an involuntarily exhale, the tip of Alec’s tongue flicking out, the barest touch against the pad of Jace’s fingers, and enough to make him snap. Shaking off the last remnant of relaxation, he surged upwards, slinging his arms around Alec’s neck and claiming his lips in a hungry kiss.

After a second’s hesitation Alec responded in kind, strong arms hauling Jace closer until he was perched in Alec’s lap, naked skin pressed against Alec’s clothed body, tremors of want shooting through him when Alec’s hands began exploring his back. Jace rocked forward, hissing when he felt Alec’s hardness through the fabric, then pushed backwards into Alec’s grip, and Alec groaned when a gush of slick coated his fingers. He stopped kissing Jace, sucking and licking along Jace’s jaw, catching his earlobe with his teeth, making Jace curse and tighten the grip he had on Alec’s hair.

They were rocking together now, bursts of pleasure racing over Jace’s skin, heat curling tightly in his belly, but while at any other time Jace was a big fan of leisurely make-out sessions, right now he needed _more_. Letting go of Alec’s hair, he impatiently pulled at his friend’s sweater, forced him to let go of Jace long enough to take it off. Sitting back on his haunches, Jace watched every bit of skin being revealed with hungry eyes, licking his lips in anticipation and curling his hand loosely around the base of his cock.

Freeing his head, Alec saw what he was doing, and the next moment Jace found himself pushed onto his back. He barely had time to protest when Alec gave him a challenging grin, familiar from years of sparring together, and leaned down to take Jace’s cock in his mouth. Bucking in surprise, Jace cursed, gripping Alec’s shoulders for support, his friend making up for any lack of experience with great enthusiasm. 

The heavy mix of their scents mingling in the air between them helped, too, of course, pheromones and sex, and Jace could feel himself soak the mattress even before Alec slid a pillow under his ass. If the older boy felt nervous, he didn’t show it except in the way he kept glancing up through dark lashes to check for Jace’s reaction. 

If touching himself earlier had felt good, having Alec insert two long fingers into his waiting hole was _heaven_ , and Jace pushed eagerly into the touch, tightening his muscles, laughing breathlessly when Alec jerked up and _bit down_ at the juncture of Jace’s neck and shoulder. The motion robbed Jace’s cock of its hot, wet resting place, but Jace couldn’t care, not when the sensation of blunt teeth digging into his flesh erased all traces of amusement, replaced by a primal urge that made Jace beg, “Yes, please, _Alec_!”

His erection dragged against the hard planes of Alec’s stomach, catching at the elastic of his sweat pants, and Jace blindly groped for the edge of fabric, pushed it downwards clumsily. The alpha huffed against his neck, one hand still buried inside Jace, and lifted his hips, using his free hand to finally slip out of pants and briefs. Then they were both naked, their cocks sliding together, and Jace groaned and wrapped his legs around Alec’s middle, trapping him against his body.

The moved against one another awkwardly, but it still felt better than anything Jace had ever experienced, even before Alec growled in frustration and removed his hand from Jace’s body, gripped his thighs and sat up. This brought the head of his cock in perfect alignment with Jace’s ass, and Jace felt another gush of slick leave him, his body aching to be filled, _taken_ in a way that would have humiliated him if his partner had been anyone but Alec.

Despite his visible arousal, fluid perling at the head of his cock, a flush working its way down his chest, the alpha had paused, looking down at Jace consideringly. Then he tilted his head and _flipped_ Jace over, leaning forward before the omega could protest and placing an almost reverent kiss against the scent gland at the back of Jace’s neck. “I think it’ll be easier that way, the first time at least.” A rueful chuckle escaped him, one that Jace could feel rumbling through his chest. “After all, neither one of us has ever done this before.”

“Well, however you decide to do it, just fucking _do it_!” Jace knew he was sounding petulant, but his skin was on fire and Alec’s body was plastered against his back, his proximity filling Jace’s senses, making him want things, _omega_ things. And because patience had never been one of Jace’s virtues, he managed to get to his knees and rocked backwards. He was immediately rewarded by Alec cursing softly into his ear when his cock slid against Jace’s ass. The alpha sat up, and before Jace could protest the loss of contact, Alec’s hands were sliding down his back, over his sides, and gripped him by the hips. Jace stilled, forgetting to breathe as the blunt head of Alec’s cock, slick with a mix of both their juices, pressed against him, _into_ him. 

Alec was moving slowly, agonizingly so, and a glance over his shoulder showed Jace that his friend was taut like a bowstring, eyes fixed on the place where his erection was disappearing into Jace’s body inch by inch. Releasing a deep breath, Jace fought the urge to roll his eyes, knowing that Alec was just trying not to hurt him. However, while this might be Jace’s first time getting fucked, he was an omega in heat, he’d been ready for this for what felt like forever, and with an impatient grunt, Jace pushed backwards, impaling himself on the alpha’s cock.

“Fuck, Jace!” Surprised, Alec fingers tightened on his hips, digging in deep enough to leave marks, small pinpricks of pain-pleasure that were almost drowned out by the indescribable sensation of being filled, stretched, _complete_. This was what his body had been clamoring for, and Jace hid his face against his forearm, not wanting Alec to see how overwhelmed he was, how right this felt, like jumping off a cliff and coming home all at once. To distract himself he propped himself up on his elbows and rolled his hips, a motion that sent waves of pleasure through him and managed to cut his eyes at Alec in what was a clear challenge. 

A growl escaped Alec in response, all possessive alpha, and Jace shivered and braced himself. He was not disappointed, Alec beginning to move in earnest now, sliding in and out of the tight heat of Jace’s body with increasing force. Every thrust felt like fireworks, stoking the flames of Jace’s heat until he was a mindless bundle of _need_ , moaning and trembling, barely managing to stay on hands and knees as Alec fucked him into oblivion. In what felt like no time at all he came with a low cry, untouched, cock twitching against his stomach, spurt after spurt of cum coating his chest and the bed, and if Alec hadn’t slid a steadying arm around his middle, Jace would have face-planted into the sticky mattress.

As it was, he fell limply backwards into Alec’s embrace, head lolling against the alpha’s shoulder, shivering while Alec’s free hand gently stroked his face, his arms, his chest, calming and anchoring him even as he was still being stretched open by Alec’s cock. When his senses recovered, he realized that his friend was whispering into his ear, words of endearment and praise so full of intimacy and _love_ they curled around Jace’s heart, made him feel open and vulnerable in a way the sex hadn’t. Craning his neck, he swallowed the words with his mouth, pushed them back with this tongue, and Alec went along with it easily, and they kissed until Jace’s neck began to ache.

All the while Alec remained sheathed inside him, as if that was where he belonged, and soon Jace could feel the first embers of renewed arousal spark in the place where they were connected, heat quickly spiraling outwards. Gripping Alec’s arm for purchase he tightened his muscles and lifted himself slightly only to drop and be filled fully again. Alec groaned, a sound that vibrated through them both, and began thrusting upwards, meeting every one of Jace’s movements, sending lightning pleasure racing through him with every slide of cock over sensitive nerve endings, until they were both panting and gasping.

Jace was fully hard again, but he could tell Alec was getting close, too, the tell-tale bulge of his knot beginning to push at the rim of the omega’s hole. It was strange and slightly unsettling, even more so than being fucked had been; however, Jace found himself craving it, wanting to be plugged and filled. He knew that was his biology talking, but he couldn’t bring himself to care, not when Alec was beginning to tremble, his thrusts becoming erratic. The alpha managed to growl a warning and began to pull out, obviously intent on sparing Jace his knot.

“No!” The exclamation surprised them both, Jace impaling himself to the hilt while clamping down on Alec’s cock. “Alec, I… I want…”

He couldn’t see Alec’s reaction, but he could feel his friend’s body tensing, one hand coming down to curl around Jace’s cock. Then blunt teeth dug into the back of his neck and Alec exploded inside of him. Jace cursed, pleasure shooting through him, so blinding his whole world whited out for a second as he was knotted, _owned_ , shaking so hard Alec had to roll them to the side or risk his knot catching painfully at the rim of Jace’s opening. Alec was trembling, too, his teeth pressing hard against Jace’s scent gland as he filled Jace with what felt like a never-ending orgasm. Jace was lost in the moment, his entire world narrowed to the feeling of Alec locked inside him, his alpha scent enveloping him as securely as his arms did, and for a tantalizing second Jace wanted nothing more than to remain like this forever.

Then Alec let go of his neck, a warm tongue bathing the mark he’d undoubtedly left, and Jace regained enough of his senses to stop himself from blurting out something he would later regret. Instead he rolled his hips, testing the knot, and chuckled when Alec groaned slightly. “Scoot over, the sheets are disgusting!”

“Sorry, let’s just move a bit.” Alec placed another unnecessarily apologetic kiss to the nape of his neck, and they managed to find a slightly less sticky spot while they waited for Alec’s knot to deflate. As Jace’s heartbeat slowly returned to normal, he dimly realized that he was in a completely vulnerable and exposed position, but before it could turn into proper discomfort, Alec pulled a blanket over them. Then he leaned over and coaxed a kiss from Jace, sweet and slow, a lazy exploration that lacked the urgency of their earlier exchanges. Relaxing almost in spite of himself, Jace let himself be surrounded by the warmth of Alec’s mouth, the weight of his arms and the comforting scent of satisfied alpha. He fell asleep with Alec still buried inside him.

When he woke up, they were no longer locked together, and Jace was pleasantly sore and more relaxed than he could ever remember feeling after a sexual encounter. But then, neither one of his previous conquests - an experienced female Seelie and a Nephilim girl his own age in Idris - had been a male alpha, and he hadn’t been in heat. However, deep down Jace knew that the bone-deep contentment that kept him curled around his bed partner had little to do with either and everything to do with the fact that said bed partner was _Alec_.

He was surprisingly clean, so at some point the alpha must have gotten up and washed him, a small gesture of tenderness that made Jace’s heart clench uncomfortably. A dull ache at the nape of his neck reminded him of the lightning pleasure that had shot through him when Alec bit him, and for a moment he pictured what it would feel like if he asked Alec to bite him _properly_ , to dig sharp alpha teeth into his scent gland and mark him for real, to claim Jace as his omega mate… Despite his heat having already dissipated, which was common for a first cycle, Jace could feel the first embers of renewed lust curl in his stomach, paired with something much, much more frightening.

Resolutely ignoring the part of himself that wanted nothing more to _belong_ to Alec the way only an omega could, Jace sat up abruptly, waking the alpha in the process, and Jace had to stop himself from reaching out and carding his fingers through sleep-mussed hair. Instead he put on a bright smile and said lightly, “Hey, good morning - looks as if my heat has passed, so thanks for your help.”

Swinging his legs over the edge of the bed, he ignored the way Alec’s eyes narrowed in suspicion as he shook off the last remnants of sleep and finally replied in a carefully bland voice, “Sure. It’s not as if it was a hardship.”

“Of course not - who wouldn’t want a piece of all of this!” Gesturing over his body, Jace managed a cocky smirk and got up, although every fibre of his being wanted to slide back into bed, into the warm cocoon of Alec’s arms. But that was his weak omega side talking, and it was no longer in charge, so instead he pulled on some fresh clothes from a nearby drawer, ignoring the part of him that went all warm and melty at the thought of wearing Alec's things. He even managed to chat nonchalantly, “I really appreciate your help, and maybe we can do it again next year when I have to stop the suppressants for one cycle. It wasn’t half-bad - for sex with an alpha, I mean… Sorry, dude, but that’s not something I’d want every day.”

Realizing he was babbling, Jace forced himself to stop and finally looked back at Alec, who was regarding him from hooded eyes. All trace of the previous sleepy relaxation had disappeared from his long limbs, and he had drawn his knees to his chest, hugging them in what Jace figured was supposed to be a casual gesture but only made his heart ache stupidly with the desire to smooth away the tension in Alec’s handsome face. 

_Handsome_. Jace shook himself; he really needed to get a grip on those treacherous omega thoughts. The bite mark on his neck throbbed, and he knew with sudden clarity that the next time he wouldn’t be able to stop himself, would bare his throat and beg for a proper mate mark. And Alec would do it, and they’d be connected forever, only not in the way Jace had always imagined, two equal warriors fighting side by side but with Jace as nothing except Alec’s omega mate. Mated pairs couldn’t become parabatai, eros being forbidden by both Law and custom.

Rationally Jace knew that the nausea that rose in his throat at the thought was a result of his father’s twisted teachings. However, while he’d more or less come to terms with his nature and accepted that being an omega didn’t automatically make him weaker, asking for Alec’s mark felt like giving in, like subjugating himself, and that was simply unacceptable. So he pushed aside that small voice and sat down next to his alpha friend, trying not to scent the air around him, which was still heavy with pheromones and the musk of sex, his and Alec’s comingling most temptingly. 

Instead Jace steeled himself and met Alec’s gaze, which already seemed withdrawn and resigned, entirely unlike the open, passionate way he’d looked at Jace just a few hours ago, when they were locked together. But they could still have this, if they synced up Jace’s annual heat with Alec’s rut, and Jace was proud of how steady he sounded as he asked, “Alec, I’ve been meaning to ask this before - will you be my parabatai?”

He’d always pictured this as a happy moment, cementing a relationship he couldn’t imagine doing without, but although Alec quickly hid it, he’d looked _stricken_ , and once again Jace cursed who and what he was. He forced a smile and covered Alec’s hand with his own. “We’ll be the best, you’ll see!”

It was the truth, but the words tasted like ashes in Jace’s mouth. Still, Alec would be his, and he would be Alec’s, and that was all that mattered.

***

**Six years later**

As far as Clary was concerned, finding out she had a secondary gender ranked way up on the weirdness scale. Apparently the magics her mom had used to suppress her nature were very strong and expensive, but they’d been broken, and now her body was doing strange new things, because she was apparently something called an _omega_.

Izzy had assured her that she’d get used to it, at least once she’d had her first heat, but the amused quirk of Alec’s mouth made her suspect that this first hurdle wasn’t as easy to take as his sister made it sound. She wasn’t quite sure why, but the tall, dark-haired Shadowhunter obviously didn’t like her, so anything that made him exchange not-so-secretive smirks with Jace was bound to spell discomfort for her.

Luckily Jace seemed to sense her worry, because he turned from his parabatai and reassured her, “Izzy might not know exactly what a heat means, being a beta and all, but she’s right, you’ll be fine.”

“Can you help me with… with the heat?” Clary asked, hating how unsure she sounded. A bark of laughter escaped Alec, and Jace swatted him reprovingly, but Clary noticed a flush creeping into his cheeks. 

“Don’t be an ass, Alec.” Clearing his throat, he explained, “Only an alpha can help an omega in heat. By… having sex with them.”

Realization of what she’d just asked him dropping like a lead balloon, Clary blushed hotly and was grateful when Izzy added matter-of-factly, “Unmated omegas can ask an alpha friend, or get the services of a professional support alpha, but really, you don’t _have_ to have sex during your heat. That would be barbaric!”

Jace stepped closer, his fingers cool on her cheek as he forced her meet his mismatched eyes, which were warm and full of understanding, reminding her why he was the one person in this crazy new world she trusted. Ignoring the two Lightwoods he gave her a charming, sincere smile that set loose a flutter of butterflies in her stomach, keeping his voice low and deliberately light as he explained, “I’d be honored to help you, Clary, but I’m an omega, too.”

“Umm, I see...” Clary was aware that her face probably matched her hair right now, but she forced herself not to look away from Jace’s gaze until a cough from Isabelle broke the moment.

“You should feel special, he doesn’t tell just anybody,” the beta said with a smile, and once more Clary felt grateful for the other girl’s friendship, which had been so freely offered. Unlike her brother, whose scowl Clary could have sworn hid pained resignation.

Feeling brave, she asked Jace, “What do _you_ do?”

“Well…” Blushing uncharacteristically, Jace lifted a hand and rubbed at the back of his neck, where for the first time Clary noticed a set of half-healed bite marks. “Alec usually helps me through my heats.”

“Oh. I see.” Clary felt unexpectedly disappointed. Jace owed her nothing, after all she barely knew him, and yet there’d been this connection between them right from the start. “Are you… are you _mates_?”

“No,” Jace replied quickly. “Even if we were, you know, _like that_...” He shot Alec a look heavy with years of shared experiences that Clary couldn’t even begin to grasp before looking back at her. “It’s okay to help each other out, but mate-bonds aren’t allowed between parabatai. And I don’t want an alpha anyway.” He forced out a laugh, a harsh, cold sound that made Alec visibly flinch, although he quickly covered it up, and Clary’s heart contracted in sudden sympathy. “They’re more trouble than they’re worth.”

Out of the corner of her eye Clary noticed Izzy narrowing her eyes at Jace and reaching out to her brother, but Alec moved away from her comforting touch, staring fixedly at the ground, shoulders hunched, face a mask. Tilting her head in consideration, Clary nonetheless just nodded non-committally at Jace. “I see.”

And she did see, even before the memory demon made it obvious to everyone else. Less obvious was the way Jace’s posture stiffened when Magnus Bane flirted with Alec, but Clary had always been good at seeing through people’s facades, and later that night she tried to put to paper what she’d glimpsed in Jace’s face for just a second: jealousy and a longing so deep it made Clary blush.

Jace might not want an alpha, but he most certainly wanted Alec Lightwood.


End file.
